The present invention relates to a printing apparatus and a control method therefor and, more particularly, to a printing apparatus for printing by reciprocally moving a carriage on which an inkjet printhead is mounted and a control method for the printing apparatus.
A printing apparatus used as a printing unit for printing an image and the like in a printer, copying machine, facsimile apparatus, or the like, or as a print output device for a composite electronic device or workstation including a computer and word processor is designed to print an image and the like on the printing medium such as a paper sheet or thin plastic plate on the basis of image information (including all output information such as character information).
Such printing apparatuses are classified by their printing methods into an inkjet method, wire dot method, thermal method, electro-photographic method, and the like. Of these methods, the printing apparatus using the inkjet method (to be referred to as an inkjet printing apparatus hereinafter) implements printing by discharging ink from an inkjet printhead to the printing medium. According to this method, high-precision printing operation can be easily and quietly performed at high speed, and the cost can be low as compared to the other printing methods. Furthermore, in recent years, a color output such as a color image becomes more important, and many types of color inkjet printing apparatuses whose image quality is equivalent to halide photography have been developed.
Some of these inkjet printing apparatuses are implemented such that a printhead with a plurality of array-integrated printing elements, orifices, and ink channels is used to increase printing speed, and a plurality of printheads are mounted on a carriage in correspondence with the number of color inks to cope with color printing. These printheads are arranged side by side in the carriage moving direction (to be referred to as a main-scanning direction).
The inkjet printing apparatus intermittently discharges ink so as to always maintain a good ink discharge state independently of printing operation during intervals between printing operations (to be referred to as preliminary discharge). Such preliminary discharge can be performed at various timings. Preliminary discharge is generally performed to an ink receptor which is arranged at the reversing position of the carriage (e.g., a position near the home position of the carriage) during reciprocal movement of the carriage, particularly, when the carriage moving direction reverses.
FIG. 8 is a view showing the relationship between the speed and position of the printhead in the main-scanning direction when preliminary discharge is performed upon reversing the carriage. For the sake of descriptive convenience, consider a case where a nozzle array for discharging black ink (to be referred to as a black nozzle array) and a color nozzle array for discharging color ink (to be referred to as a color nozzle array) are arranged side by side in the main-scanning direction on the printhead mounted on the carriage.
In FIG. 8, reference symbol v denotes the moving speed of the black nozzle array and color nozzle array in the main-scanning direction; x, the position of the black nozzle array and color nozzle array in the main-scanning direction; and Y, a preliminary discharge position (ink receiving position). Reference numeral 301 denotes a solid line indicating the moving speed and position of the black nozzle array; and 302, a dotted line indicating the moving speed and position of the color nozzle array. Reference symbols I1 and I2 denote printing areas; Ie1 and Ie2, end portions of the printing areas; Kd, the deceleration start position of the black nozzle array; Cd, the deceleration start position of the color nozzle array; Ka, the acceleration end position of the black nozzle array; Ca, the acceleration end position of the color nozzle array; Ck, the position of the black nozzle array at a time of the preliminary discharge of the color nozzle array; and Kc, the position of the color nozzle array in the preliminary discharge of the black nozzle array.
With regard to the main-scanning direction, the interval between the color nozzle array and the black nozzle array corresponds to the interval between Cd and Kd. Likewise, the interval between Ck and Y, interval between Y and Kc, and interval between Ca and Ka respectively correspond to the interval between the color nozzle array and the black nozzle array.
The reciprocal movement of the black nozzle array and color nozzle array in the main-scanning direction will be described in detail below with reference to FIG. 8.
(1) In a constant speed movement zone on the right side (area I2) of Ie2, or on the right side (area I1) of Ie1, printing operation is performed by using the black nozzle array and color nozzle array.
(2) With regard to a backward movement, the black nozzle array moves at a constant speed between Ie1 and Kd, and the color nozzle array moves at the constant speed between Ie1 and Cd.
(3) With regard to the backward movement, the black nozzle array decelerates between Kd and Y, and the color nozzle array decelerates between Cd and Ck.
(4) The black nozzle array stops at Y, and the color nozzle array stops at Ck, from the start to the end of the preliminary discharge operation of the black nozzle array.
(5) The moving direction of the carriage is reversed, and then the forward movement is started from this point. The black nozzle array moves between Y and Kc, and the color nozzle array moves between Ck and Y, in the forward direction until the color nozzle array reaches the position where preliminary discharge can be performed, i.e., an ink receptor""s position, accompanied with slight acceleration and deceleration.
(6) The black nozzle array stops at Kc, and the color nozzle array stops at Y, from the start to the end of the preliminary discharge operation of the color nozzle array.
(7) With regard to the forward movement, the black nozzle array accelerates between Kc and Ka, and the color nozzle array accelerates between Y and Ca. Note that Ka and Ie2 indicate the same position.
(8) With regard to the forward movement, the color nozzle array moves at a constant speed between Ca and Ka. In this case, since the black nozzle array has reached the end portion Ie2 of the print area, the black nozzle array performs printing operation while moving at the constant speed.
(9) With regard to the forward movement, the color nozzle array also moves at the constant speed and performs printing operation after reaching the end portion Ie2 of the print area.
In performing preliminary discharge according to the above procedure when the moving direction of the carriage is reversed, the carriage may not achieve sufficient acceleration in the acceleration regions, (Y-Ca) and (Kc-Ka). If the carriage cannot accelerate sufficiently, the carriage cannot move at a desired speed or the constant speed or may vibrate, even when the carriage reaches the print area, thus posing a problem.
In order to solve the problem, the acceleration regions may be extended so that the carriage can achieve sufficient acceleration. This, however, results in an increase in the width of the printing apparatus main body.
For example, Japanese Patent Publication Laid-Open No. 6-115097 discloses an arrangement where the ink receptor for preliminary discharge is set at the accelerate/decelerate start position of the carriage. In the arrangement where two arrays of the printheads are juxtaposed in the main-scanning direction, when the ink receptor does not have a sufficient width for the simultaneous preliminary discharge of the two arrays of printheads, the above problem may occur depending on the order of preliminary discharge.
Japanese Patent Publication Laid-Open No. 10-309810 discloses a technique of performing preliminary discharge while moving the carriage. In order to discharge ink to the ink receptor for preliminary discharge correctly, the number of ink droplets for the preliminary discharge must be limited, or the ink receptor with a width corresponding to the required number of the ink droplets must be installed. If preliminary discharge is not sufficiently performed, print quality deteriorates. If a sufficient width for discharging ink is provided, the width of the printing apparatus main body becomes large.
As described above, in the prior art, when the preliminary discharge is performed when the moving direction of the printhead is reversed, the above drawbacks remain unsolved.
Accordingly it is an object of the present invention to provide a printing apparatus and a control method therefor which can ensure a sufficient acceleration area for stable movement of a carriage and achieve downsizing.
According to one aspect of the present invention, the foregoing object is attained by providing a printing apparatus for printing by discharging ink from an inkjet printhead to a printing medium by using the inkjet printhead on which a plurality of nozzle arrays each having a plurality of nozzles for discharging ink are arranged in a direction different from an array direction of the nozzles while reciprocally moving a carriage on which the inkjet printhead is mounted in a direction in which the plurality of nozzle arrays are arranged, comprising: scanning means for reciprocally moving the carriage; an ink receptor, being arranged on at least one end of a reciprocal movement area of the inkjet printhead, for receiving the ink discharged from the inkjet printhead; preliminary discharge driving means for performing preliminary discharge from the inkjet printhead to the ink receptor when a carriage moving direction in the reciprocal movement is reversed by the scanning means; scanning control means for controlling the carriage to stop in the preliminary discharge, accelerate from zero speed to a predetermined speed after the preliminary discharge is completed, and move at the predetermined speed; and control means for controlling movement of the carriage by the scanning means and the preliminary discharge performed by the preliminary discharge driving means such that the preliminary discharge is sequentially performed with regard to the plurality of nozzle arrays from a nozzle array arranged outside the reciprocal movement area to another nozzle array inside the area.
The ink receptor is preferably arranged near the home position of the carriage. Additionally, another ink receptor may be arranged at one end of a reciprocal movement area of an inkjet printhead, which is located on the opposite side to the home position.
The plurality of nozzle arrays may be nozzle arrays for respectively discharging different color inks.
The print area in which the inkjet printhead discharges ink to print is set inside the reciprocal movement area. The distance from the position of the ink receptor to one end of the print area is sufficient for the carriage to reach a predetermined speed.
Additionally, the inkjet printhead preferably includes an electrothermal transducer which is used for generating thermal energy to be applied to the ink in order to discharge the ink by using the thermal energy.
According to another aspect of the present invention, the foregoing object is attained by providing a print control method adapted to a printing apparatus for printing by discharging ink from an inkjet printhead to a printing medium by using the inkjet printhead on which a plurality of nozzle arrays each having a plurality of nozzles for discharging ink are arranged in a direction different from an array direction of the plurality of nozzles while reciprocally moving a carriage on which the inkjet printhead is mounted in a direction in which the plurality of nozzle arrays are arranged and printing, and performing preliminary discharge from the inkjet printhead to an ink receptor arranged on at least one end of a reciprocal movement area of the inkjet printhead, comprising: a preliminary discharge step of performing the preliminary discharge from the inkjet printhead to the ink receptor when a moving direction of the carriage is reversed; a scanning control step of controlling the carriage to stop in the preliminary discharge, accelerate from zero speed to a predetermined speed after the preliminary discharge is completed, and move at the predetermined speed; and a control step of controlling movement of the carriage and the preliminary discharge performed at the preliminary discharge step such that the preliminary discharge is sequentially performed with regard to the plurality of nozzle arrays from a nozzle array arranged outside the reciprocal movement area to another nozzle array inside the area.
In accordance with the present invention as described above, an inkjet printhead reciprocally moves, on which a plurality of nozzle arrays for discharging ink are arranged in a moving direction of a carriage. Preliminary discharge is performed from the inkjet printhead to an ink receptor arranged on at least one end of a reciprocal movement area of the inkjet printhead when the moving direction of the carriage is reversed. The scanning of the carriage is controlled so that when this preliminary discharge is to be performed, the carriage stops, and that the carriage accelerates from zero speed to a predetermined speed after the preliminary discharge is completed, and moves at the constant speed. On the other hand, with regard to the plurality of nozzle arrays, the movement of the carriage and the preliminary discharge are so controlled as to sequentially perform the preliminary discharge from the nozzle array arranged outside the reciprocal movement area to the nozzle array arranged inside the area.
The invention is particularly advantageous since the sufficient acceleration area for stable movement of the carriage can be ensured without extending the carriage acceleration area.
Therefore, the present invention can make the carriage movement stable, keep the image print quality high, and contribute to the downsizing of the printing apparatus.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.